1. Field
The present disclosure relates generally to aircraft and, in particular, to fluid flow for an aircraft. Still more particularly, the present disclosure relates to a method and apparatus for controlling the aerodynamics of an aircraft using a flow control actuator having a variable frequency.
2. Background
In operating an aircraft, fluid flow control systems may be used for desired operation of the aircraft and the components within or on the aircraft. These fluid flow control systems may be used during different phases of operation of the aircraft. For example, these systems may be used during take-off, in flight, landing, taxiing on the runway, or during other phases of operation while the aircraft is in service. These fluid flow control systems may be used to control the flow of fluid over, in, or through various portions of an aircraft during these phases of operation.
Flow control actuators may be used in a fluid flow control system to maintain a desired flow of a fluid such as air. These flow control actuators may be used to maintain a desired flow of fluid in an aircraft for many different purposes. For example, flow control actuators may be used in jet inlet and exhaust systems, environmental systems, control surface systems, and other systems in an aircraft. Flow control actuators may be used to maintain desired boundary layers on control surfaces, to reduce noise, or to control fluid flow for other suitable purposes within the aircraft.
A currently used flow control actuator may take the form of a fluidic oscillator. This type of flow control actuator is designed to produce a flow of fluid moving in a sweeping manner from side to side at an output port of the flow control actuator. These oscillations of fluid flow occur at a particular frequency. The fluid flow output by a fluidic oscillator that moves in a sweeping manner may be referred to as a sweeping jet.
Changing the frequency of the flow of fluids sweeping from side to side to control fluid flow in a particular system may be desirable in some cases. This frequency may be changed to provide a desired fluid flow for a particular aircraft structure by changing the flow rate of fluid into the fluidic oscillators. Currently, the frequency of the flow of fluid out of a fluidic oscillator may be changed by replacing the fluidic oscillator with another fluidic oscillator. Replacement may be undesirable when dynamic control of fluid flow by the fluid flow system is desired.
Further, the frequency of oscillations in fluidic oscillators may be changed during operation of the fluidic oscillator by altering the supply pressure of the fluid to the fluid oscillator. However, in some cases, changing the fluid flow through the fluidic oscillator may not be desirable. For example, changing the fluid flow may use more energy than desired in the source of the fluid flow for the fluidic oscillator. In other cases, increased maintenance may be needed for the fluid source supplying fluid to the fluidic oscillator. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.